i think those breeder boxes are awful, they should come with instructions that the fish should be kept in their for a maximum of xxx hours
wilder has the right idea with lots of plants, especially floating plants. in my experience the babies hover near the surface in the roots of floating plants, then you can easily scoopt hem up.
OR if you have a seperate tank for fry, transfer the mom over before she gives birth, let her have them in the fry tank then put her back in the main tank after shes done.